Watch your head, you don't want it hit by return fire in the ever-present MMO blogosphere discussion of fantasy vs sci-fi. The most recent discussion started up with Massively's own Michael Zenke and his "Five Reasons Sci-Fi Pwns Fantasy" which prompted the return fire in question from Grimwell. Both of the posts are certainly worth reading, especially if you have any kind of lingering interest in the subject matter.
As far as we can see, there's truth to be had on both sides of the fence. However, we do have one point of contention to make with Grimwelll's argument. He states that the reason fantasy "pwns" sci-fi is that it's accessible, which is a constant argument on the matter. While we think he may have a point in that less people are inherently familiar with sci-fi, we very much disagree with his assessment that you need to be a math nerd to enjoy good sci-fi -- his example in this case being Star Trek and its now-infamous technobabble.